Method of electroforming molds



' Filed Aug. 1, 1949 Jan. 16, 1951 0. L MILTON, JR., ETAL 2,538,160

METHOD OF ELECTROFORMING MOLDS Q 4 Sheets-Sheet 1 Fig.1. I

GELLED AL NATE RESINOUS POSITIVE OFHAND F/ WITH MOLTEN WAX SOLIDIF/ED WAX CORE 3 CONDUCT/V5 a COAT/N6 GELLE'D ALG/IVA'IE' 3mm Clare L. Milfon, Jr:

1 Car/ AN/e son W jm m Jan. 16, 19 51 Filed Aug. 1, 1949 4 Sheet$-Sheet S N n m A w w. w m" a" a O m m. c.

m m E g m. J m" v Pu E LAC 8 UER COATING RUBBER TUBE v///////////// 2 7/22 n/////////////////////w Jan' le, c L. MILTON JR" ETAL METHOD OF ELECTROFQRMING HOLDS Filed 9 4 Sheets-Sheet 4 F-I FJO.

INSULATION LACGUER LACQUER Fig-J2.

WAX CORE REMOVED RESIN POSIIT'IVE cum/ 351) ELECTRO- news/rm NIGKEL FDR MOLD Patented Jan. 16, 1951 METHOD OF ELECTROFORMING MOLDS Glare L. Milton, J12, Roslyn Heights, N. Y., and Carl A. Nielsen, Takoma Park, Md, assignors to the United States of America as represented by the Secretary of the Army Application August 1, 1949, Serial No. 107,978

(Granted under the m of March 3, 1883, as

amended April 30, 1928; 3'70 0. G. 757) 4 Claims.

The invention described herein may be manufa-ctured and used by or for the Government for troforming. If, in addition, a moderately strong or dense deposit of a high-melting metal is required, and the object to be reproduced is of such a shape that not all of the areas can be sprayed at an angleof approximately 45, satisfactory molds can be produced only by casting, or by electroforming.

The present invention relates'to a method of electroforming a mold which is particularly advantageous in the casting of a natural-appearing glove for covering a prosthetic hand, or in any application wherever major undercuts are encountered.

The process of the present invention comprises conducting the electroforming over a hollow, flexible' model of the object to be reproduced by the mold, the interior cavity of the moldduplicating in high fidelity thesurface'details of the object to be duplicated, the said model being filled with a readily removable; rigidifying core capable of being dissolved, softened, or melted, to the extent-that it maybe removed at a temperature below the temperature of decomposition or melting of the hollow flexible model, or the temperature at which appreciable distortion of the electro-- formed mold would take place.

For example, there is shown in the accompanying drawings a series of steps employed in the making of a mold for, the production of such seamless gloves, in which the characteristics of size, contour and surfacev details of a natural hand are reproduced in high fidelity; and while the inventionis not limited necessarily to such embodiment, the invention was developed with such embodiment as its primary aim and purpose.

It is apparent that when anindividual has lost one or. both hands and is fitted with an artificial hand as .a prosthetic device, for replacement of the missing member, there is afforded an im-a portant uplift in morale if the prosthetic appliance can be rendered inconspicuous to anobserver. The usual kid gloves employed asthe conventional coverings for such artificial hands only serve to advertiseto-the public the deformity of the wearer. The process of the present invention provides, among other things, the production of a glove for such purpose that renders the artificial hand indistinguishable to an observer from a natural hand.

In order to accomplish such a desirable result, certain procedures must be followed, and as ap plied to the production of a glove which is virtually indistinguishable-from a natural hand; the process ofthe inventioncomprises the following general steps:

1. The formation of an initial impression of a selected model hand of an individual whose natural hands match insize and shape, asclosely as possible, the natural hand of the amputee. Thus, if the amputee isaunilateral amputee, that is, one who has lost only one hand, the remain ing hand is matched as closely'as possible as to size and shape by the hand of an individual who is selected to serve as a model. Thus, if the right hand of the amputee is missing, there is selected as a model an individual whose natural right hand matches the size and contour ofathe amputees left hand as closely-as possible. If the amputee is bilateral, i. e., has lost both hands, such a close matching of size andcontour is'not so important and the initial impression is made of both hands of the individual chosen as the model.

2. The initial impression of the models hand duplicates the shape and surface characteristics of that hand. When the impression has been formed, the hand is removed, and the resulting cavity is filled with a selected resinous composition which is liquid when introduced into the impression, but which can be coagulated or geiled readily on the surfaces of the impression. The ungelled, liquid residual resin. is removed from the impression leaving the resulting: gelled resinous skin in placev in the cavity of the original impression. This resinous skin. is a positive of the impression and his reinforced preferably before it is removed from the impression, by filling it with a rigidifying core, such as molten wax, which is allowed to solidify in the gelled resin positive. A.suitable electrode hanger is inserted in the rigidified core, and the whole assembly is removed from the original impression. The positive gelled resinous skin is made electrically conductive and is placedas cathode in an electroforming; bath,p1ielinrably an. aqueousv bath of nickel or copper salts, and electroplated with metal under controlled conditions which assure a uniform deposit of metal all over the conductive positive skin. When a suitable thickness of metal is deposited, the plated assembly removed from the bath, the wax is removed by melting and draining it out through the Wrist opening, the positive skin then is separated mechanically from the interior of the metal deposit, and pulled out through the said wrist opening, leaving the deposited metal as a seamless mold which duplicates interiorly the surface characteristics of the original model hand, and in which the final composition is adapted to be cast.

Reference now may be had to the accompanying drawings in which:

Fig. l is a diagrammatic view illustrating a model hand inserted in a bath adapted to form the initial impression which is employed in producing the mold in accordance with this invention;

Fig. 2 is a diagrammatic view showing the initial impression of the model hand, with the hand removed;

Fig. 3 is a diagrammatic View of the original impression filled with liquid resin for forming the positive;

Fig. 4 is a view similar to Fig. 3, but showing peripheral gelation of the resin in the impression;

Fig. 5 is a view similar to Fig. 4, but showing ungelled resin being removed from the initial impression;

Fig. 6 is a view similar to Fig. 5, but showing the resin completely removed from the gelled positive, which is still in the original impression;

Fig. 7 is a view similar to Fig. 6, but showing the gelled positive filled with a rigidifying core, such as molten wax;

Fig. 8 is a view showing the positive and solidified. wax core removed from the initial impression bath, with a fragment of an electrode hanger inserted therein, the resulting form being provided with an electroconductive coating;

Fig. 9 is a diagrammatic perspective view of a preferred form of plating equipment for electroforming the mold of the present invention, the view showing the electrical connections of the deposition cell;

Fig. 10 is a longitudinal, vertical, sectional elevation of the cell of Fig. 9, the view being taken on the vertical longitudinal center line of the cell of Fig. 9;

Fig. 11 is a transverse sectional plan view through the wrist portion of the form being plated in Fig. 9, the view indicating the layer of deposited metal, the rigid core material for the form being still in place;

Fig. 12 is a view similar to Fig. 11, but with the rigid core material removed, and showing the resinous positive prepared as outlined above, separated from the deposited metal and collapsed for removal from the resulting electrodeposited mold; and

Fig. 13 is a fragmentary sectional elevation of an auxiliary anode illustrated in Fig. 16, showing details of protective insulation on the anode, with electrical connection to the anode, the view being applicable to either auxiliary anode shown in Figs. 9 and 10.

Referring more particularly to the drawings, the numeral l2 represents a model hand immersed in a bath M for forming an initial impression of the hand. The bath I4 is contained in a suitable receptacle I5, and. is a gelable liquid alginate composition that is adapted to gel about the hand to form a stiff, elastic gelled mass, the hand forming an impression therein which duplicates in the surfaces of the impression all surface details of the model hand. Since is a requisite that the model hand 52 be releasable from the elastomer gelled alginate bath it without permanent distortion of the impression of the hand, the composition of this material is critical, not only because of the requisite elastic properties of the gelled material, but because of the fact that gelation of the material must be effected at a temperature sufiiciently low to prevent discomfort to the individual whose hand is serving as the model. When gelled, however, the bath must resist liquefaction at temperatures above the gelation temperature of the positive-forming resin which is to be introduced into the impression.

In practice, the bath i4 is made satisfactorily of a liquid alginate which can be obtained from kelp. It is found in practice that the material sold on the market as Cue-loid duplicating colloid material is well suitable, this colloid being a polymer of d-manuronic acid extracted from kelp. This alginate material is incorporated in an aqueous retarder solution and water, the retarder solution retarding the gelaticn of the alginate until the model hand i2 is introduced into the bath and properly positioned. The retarder solution is composed of a mixture of sodium phosphates, calcium phosphates and potassium phosphates, the concentration or" the phosphates depending upon the desired length of gelation time. Thus, for example, a hath made up in the proportions of 13.5 gms. of Coe-loid duplicating colloid (alginate), '70 cc. of retarder solution containing about equal amounts by weight of sodium, calcium and potassium phosphates to sub-- stantial saturation, and 30 cc. of water will form a stiff elasto 1.eric gel in about ten minutes at a temperature of from 35 to 40 C. ihe time of gelation canbe controlled by the amount and concentration of the retarder solution employed, the more retarder the slower the time of gelation. The d-manuronic acid may be regarded as being synonymous with alginic acid. The resulting material is sufficiently elastic when gelled to permit the model hand being withdrawn from the gelled oath without permanent distortion of the impression or injury to the detail lines corresponding to the surface features of the model hand. Upon removal of the hand, the material which is stretched during such removal returns to its original position, leaving the impression cavity It as a duplicating negative impression of the hand #2. Since the hand 12 is immersed in the bath. above the wrist portion 18, when the hand is withdrawn, the opening 2% in the cavity It returns to the size of the arm portion which was immersed in the bath while liquid. The impression it is a high-fidelity duplicate of the hand i2 down to minutest details of surface characteristics, including veins, knuckles, nails and finger print lines, the impression being, however, reversed (negative) with respect to the hand it. Withdrawal of the model hand 52 is efiected by gently working the fingers and hands loose from the encasing gel, cold water being poured around the hand during this operation, if desired, to further rigidify the gel and contract it away from the fingers and hand. Also, compressed air may be introduced into the cavity it as the hand is withdrawn in order to neutralize any tendency to form a vacuum in the cavity behind the fingers and hand as the hand is withdrawn.

. Z fl'helimpression :1 fiifOll'IlS ;a' :mol'd Eforrc-asting a .zfiexible: resinous positive :which formsthe founda- :ticn :for ;:the .iinishe'cl mold produced in accord- "The resinous'rcomposition.Hpreferably is adis- :persion .:or i polyvinyl chloride ror a copolymeraof vinyl chloride with vinyl acetate, zmethyltorsethyl :iacrylate, :methacrylate, .fumarate or maleate,

:mer-aor copolymer, containing ;at least lthirtyefive percent of chlorine, inxaesolution containingzfrom 60:5. 13.81 cent to .five'per cent of ;a "polymer or '00-- zpolymer;selectedxfrom the group above; or .a poly- :mer f one of the monomers mentionedruabove, the. balance .of the rsolutionzibeing made'wup of a .plasticizer for the chlorine-containing resin. There :may be used also compositions similarto ctheiabover in vrhich ithe chlorine-containing resin is 'dispersed in; a .plasticizercor mixture ;of plastiicizers1-a1one,:rather than. in:;a solutionof .a poly- :mer in such a :plasticizer.

' The following examples indicateeXamples zof :resinous compositions suitable for-the reproduction of the above-indicated flexible positive, a-theiproportions being parts by weight:

Example I Parts Paste, grade polyvinyl chloride-vinylacetate copolymer 100 Tricresyl phosphate Dibutyl phthalate 25 Polyethyl-methacrylate .4

J Example II Parts Paste grade polyvinyl chloride-vinyl acetate copolymer Di-Z-ethylhexyl phthalate 29 Tricresyl phosphate -29 Polyethyl -methacrylate Example III Parts Polyvinyl chloride resin Di-'2-ethylhexyl phthalateflh 26.7 "Tricresylphosphate 26.7

Polyvinyl chloride-vinyl acetate copolymer 1:5

The foregoing compositions .are free-flowing and gel at moderate temperatures, for example, .from about 69 C. .toabout 90 C. The alginate bath .M has the characteristic of being permanent at such gelation temperature of the resin. This alginate bath may be warmed to its gelation temperature of 35 to 40 C., by a source ofheat .24, if need be, for forming the initial impression.

Upon heating the bath to gelation temperature of the resin 22, the resin compositiongelsperipherally as indicated at 26, this forming a gelled resinous skin which is apositive duplicate .of the original impression it. The ungelled resin .2-2'..is removed, as by decantation or sypnoning through a tube 23, and the gelled skin, which is left undisturbed in the impression is built up "to arequisite thickness by refilling with the resinous dispersion, gelling additional resin on the skin and removing ungelled'resin as before, this procedure'being repeated as many times as maybe necessary to build up "the desired thickness of deposit. 'Ihisrepeated procedure is preferredto avoid" the possibility of over-heating the jge' led portion of the resin or the alginate'bath.

, Upon completion of the gelation, thereremains in the impressionlfi 'afragile, 'gelledpositive vviny lidene chlorideor.othermonomers, thepolyl 6 zreplica ao'f rthe iimpression tand=-.thereforej.of the priginahhand. This positiveereplica 2-6;]oeing-of ;a :fragile character, is reinforced, preferably be- :iore it is. removed from the impression, by'fllling it with molten waxes is indicated at 3ll,-which waxrhas a'lowmeltingpoint; and whichis allowed F'to-solidif y in thepositive skin i5, thereby-renderrillgthiS positive replicarigid for thednsertion of :an electrode'hanger 32, and also toenable the @positivelreplica to behandledrmore readily withiout'tearing. The rigidif-ying matrix-3wis selected i from rsuch compositions as will be removable -readilyifrom .the final mold. Preferably the wax is chosen. so that it will melt below the boiling --point,oI"--.-wa-ter. However, a mixture of such wax "with sand, or z a iwax clay mixture, or anoil-clay mixture may be usedas the rigidifying matrix. However, a sand-Wax mixture is preferred because it possesses the advantages thatrit does not shrink appreciably on cocling, thatitretainsithe sh-ape'when the fillederesinous model I is immersed :inrhotiwater, 'anrlwhen warm it is sufificientlysoft .to-permit anydesired repositioning of the model. Thus, when the flexible hollow 1nodel-25nof the .handds fil-ledwitha mixture=of sand-and wax, 'rremoved from-the alginate bath'and warmed,-the .ifingersm'ay be adjusted into whatever position-is regarded as most. desirable, and on cooling, this position is retained -in.-the now-rigid model yet in spite of this highly desirable plastic property, Lthe'mixture'of sand andwax canbewashed out .readily with "hot water. It is-desirable -for suc- --.eessful electroforming that the form-be sensibly .rigid during-the periodof plating.

When the-rigidifying core 39 has hardened, the resulting riorm isrremoved from the alginatebath 'M. This is the preferred procedure, although the invention contemplates a removal ofithecposb stiverlfi fromthe-gelledalginatebath l' i priorto filling thejpositive form with-the rigidifying material. When the :rigidifying -material has 1 hard- :ened, eitherwith' the positive 26 'still in the impression"! 6 onrernoved therefrom, the hanger 32 is inserted. ltiwill"be'understood that'when the resinous'positive 26 has'been formed in the imipression t6, the 'ai'ginatebath Hi hasrserved'its "purpose, and the destruction of the'im'pression incident, to "removal of the positive "26 is im- :materia'l.

In order "to :deposit the mold-forming metal onto the resinous positive form'26,,the surfaces thereof mustbe rendered electrically conductive. For 'this purpose, an electrically conductive coat- 111g &4 is applied to the surfaces of the positive liormlt. Thus, for example, the coating may be a verythin'layer of metallic silver applied by spraying the positive form with ammoniacal silver nitrate, thereby producing a continuous coat- 'ing of metallic silver on'the form which is at most only a few molecules in thickness for avoiding-masking any'of the fine surface lines on the positive 26.

The coating 34 is a continuous coating and is suiiiciently adherent to the resinouspositive to stay in place when the positive form is introduced into the ele'etroforming bath. The final mold metal may be any metal of high melting pointthat maybe deposited from an aqueous and which'metal is'inert to polyvinyl chlo- Thusthe preferred metal isnickel, backed, with either copper or iron.

"The production of t e final mold by electroforming operations is shown byFigs. 9 through 13 its surface rendered electrically conductive, is suspended as a cathode by hanger 32 in an electrolytic cell containing as electrolyte, an aqueous solution of the metal to be deposited. When nickel is such metal, the well-known Watts bath may be employed as electrolyte, although an all chloride type of nickel bath may be employed with excellent results, and the various addition agents used in bright nickel electroplating are beneficial in this application. Suspension of the form 40 is effected by the hanger bar 32 thrust into the wax core 30, the bar 32 being clamped to the cathode bus bar 42 by a clam 43 for intimate contact with the bus bar, the conducting surface of the form 40 being connected to the hanger bar 32 by a coil of wire 44 wrapped around the form and connected by a conducting lead 46 to the cathode hanger bar 32, as indicated by contact screw 48.

Current is supplied from plating anodes 50, 52, suspended from the anode bus bars 54, 55, these anodes being plates of the metal being deposited, the anode plates 50, 52 preferably being positioned on both sides of the form'to facilitate the production of uniform deposit of the metal on the surface of the form 40. The anodes 50, 52 are suspended from the bus bars 54, 55 by hooks 56, 58, which intimately engage the bus bars 54, 55 in the well-known manner.

Also, in order to prevent excessive thickness of metal being deposited on the ends of the form, an auxiliary cathode or thief 50 may be provided, connected by leads 52 to the cathode hanger bar 32 for stealing metal from the ends of the fingers of the form, there being thus obtained a uniform deposit of metal over the positive 26. The auxiliary cathode or thief may be simply a single wire spaced from the finger tips of the form and roughly conforming to the contour of the form. The auxiliary cathode wire 60 may be provided with a protective lacquer lay-' er 6| except for the exposed length of the wire which encloses the form. Auxiliary anodes also may be provided; for example, there may be an anode 63 between each finger of the form connected by the leads 65 to the anode lead 55, thence to the anode side of the power line through lead 61 to ammeter 68 and rheostat 10, as shown. The plating anodes 50, 52 are connected to the anode side of the power line through ammeter l2 and rheostat 14. It will be seen also that an auxiliary anode i6 is directed towards the palm of the form and spaced therefrom a suitable distance for assuring uniform deposition of the metal on the palm of the form. This anode is connected to the anode side of the power line through lead '88, ammeter 8G, and rheostat 82. Except for the desired areas for plating, the auxiliary anodes are provided with an insulating sheath, such as rubber, 84, which is lacquered as indicated at 88, the insulating coating being interrupted at 88for attachment of the leads 6'! and I8.

After completion of the electrodeposition, the form consisting of the rigidifying core 30, intermediate resin positive 26, conductive coating 34 and deposited metal 90, is removed from the plating bath. The rigidifying core is removed by melting the Wax and sluicing out with hot water, the resinous positive 26 then being collapsed as indicated in Fig. 12, and pulled out from the deposited metal through the open wrist portion thereof, the inner surfaces of the resulting metal mold accurately duplicating all details of the resinous positive.

The metal deposit 90 may be nickel only, or a multiple coating of different metals, such as nickel backed by copper. Thus, where the hollow metal form is to be employed as a mold for casting plastic cosmetic gloves, the single layer of nickel may be 0.020 inch thick, or if made of multiple coatings, a layer of nickel 0.005 inch thick may be deposited first, covering this with 0.020 inch of copper and overlaying this copper with 0.002 inch of nickel.

ing of gloves to be used as natural-appearing coverings for mechanical hands, the cast resin is to be heated in the mold at elevated temperatures for sufiicient time to cure and vulcanize the cast shape.

While the specific embodiment of the invention herein illustrated and described is applied to the production of molds shaped like'a human hand for the production of gloves duplicating a natural hand in texture, appearance, and surface characteristics, as has been described above, the process actuallyis of general application. In the production of a glove for covering a mechanical hand, it is a requisite for natural appearance, to duplicate in the finished glove all surface details of a natural hand, such as palm and finger lines, finger nails, veins and the like, which can be obtained by making the negative impression of a model human hand in the gelable liquid material and causing the liquid to gel on and around the hand while it is immersed in the solution. The resulting gelled material is sufficiently elastic to permit the hand to be withdrawn by gentle muscular movement without permanent distortion or defacement of the impressed surface characteristics of the hand, the gelable liquid being of sufliciently low viscosity to fill all surface characteristics and irregularities of the model natural hand. The liquid bath gels on standing a predetermined short time, of the order of ten minutes or less, at approximately 35 C. to 40 (7., there remaining when the hand is withdrawn, a highfidelity duplicate of the hand, as a hollow impression in the gelled bath, this impression being a negative of the hand, and being open corresponding to the wrist or arm portion of the hand, the impression duplicating the hand and as much of the wrist and arm as may have been immersed in the liquid. Accordingly, the impression and the resin positive model will be hollow and c0 extensive with the depth of immersion of the hand and arm. It is this resinous positive which is rigidified by introducing the wax-sand mixture or wax before the resin positive is removed from the gelled negative impression, and since the rigidified positive is sufiiciently tough to permit its being handled, it, together with its filling, can be removed and is electroplated as described herein to form the mold. As the metal is electrodeposited from an aqueous electrolyte, and since the deposit forms initially as a continuous mono- -molecular deposit, the finished metal mold, after the rigidifying core has been melted and drained through the open wrist portion of theform, and

the resinous positive collapsed and: removed through this same opening, duplicates interiorly all of the surface details of the original negative impression, and therefore of-the model natural hand;

It will he understood that the form being plated may not be the shape of a human hand, but can be of any other shape; and the particular configuration of the object being plated isdeterminative of the number, arrangement, and composition of the electrodes, and also the compos-h tion of the plating bath. It is necessary, how ever, that the model being plated is flexible, hollow, and open, so that the'rigidifying core can be removed through the opening, and themodel collapsed away from the electrodepositedcoating:

andzpulled out through that opening. It will be understood that the portion. of the rigidifying core which. fills theopening in the flexible model will not be plated, so that-the-continuity ofthe plating will be interrupted to this extent, and there is left an opening through which the core material when liquefied can be drained; and such, opening permits access to the flexible resinouspositive for separation thereof fromthe deposited metal and withdrawal thereof from the hollow interior of the deposited metal which is left as a hollow, seamless, one-piece metal mold inte riorly, duplicating in high fidelity all of the surface details of the flexible positive. V

The metal of the mold is dependent on the composition of the final cast product, as hasabeen mentioned above. Thus, if the final composition is nota chlorine-containing resin, the mold may be composed of electrodeposited copper. Choice of metal is determined by inertnes s to the final composition to be cast in the mold, the refractoriness of themetal to heat (resistance to melting and oxidation) andease of deposition from aqueous electrolytes.

Where a glove duplicating a natural'hand is being made, the wax core of the form is exposed at the wrist or arm opening in the resin positive, and this exposed end of the rigidifying core is not conductively coated, so that the e1ectrodepos= ited metal is interrupted to form-an opening in the deposited mold corresponding to this exposed wax, the resulting opening permitting drainage of the molten core, and removal'iof. the resin positive. in the case of other forms, the electrofor covering prosthetic hands, the steps whichcomprise immersing. a model natural hand in a congealable liquidv alginate composition which forms a stiff, elastic 'gel when congealed, congealing the compositionaloundthe-hand and adjacentarm portions, thereby producing an impression in the congealed alginate gel which-duplicates all surface characteristics of the model hand, removing the hand from the impression without permanently distorting theimpression and lines therein duplicating the surface characteristics of the modelhand, producing an open,

flexible positive=of the modelhand from the said impression by filling the impression .witha congealable liquid resinous compositionincluding a polymerized vinyl resin dispersed'in a plasticizer therefor, and which gels at a temperature below the liquefyingtemperatureof the alginate toform a flexible, elastic gel, congealing the resin onthe periphery of the impression, removing residual ungelle'd resin from the impression while leaving the resulting flexiblepositive in the said impression; filling the resultingopen, seamless, flexible ible positive can'be removed,,and removing the deposited metal isinterrupted by stoppingoff or masking a portion of the form being coatedLtomake the electrodeposited metal discontinuous over such predetermined areas for providing an opening for the removal of the core and positive.

The process of this invention includes the foregoing manipulative steps generally, as well as the steps and critical factors involved in the application of the process to the production of prosthetic gloves duplicating in high fidelity detail the texture and appearance of a natural hand. It will be apparent, therefore, that it is intended and desired to embrace within the scope of this invention such modifications and changes as may be necessary to adapt it to varying conditions and uses, as defined in the appended claims.

The present application is a continuation-inpart of copending application Serial No. 5,712, filed February 2, 1948, for Process for Making Molds, now abandoned.

Having thus described our invention, what we claim as new and wish to secure by Letters Patent is:

1. the p oduction Qi seamless cosmet c E OV core and flexible positive from the electrodepos ited metal through the said opening, thereby leaving a hollow seamless, open metallic mold interiorly duplicating the surface characteristics of the original model-hand.

2. In the production of seamless cosmetic gloves for covering prosthetic hands, the steps which comprise immersing a model natural hand in a congealable liquid alginate composition which forms a stiff, elastic gel when congealed, congealing' the composition around the hand and adjacent arm-portions, thereby producing an impression in' the congealed alginate gel which duplicates'all surface characteristics of the model hand, removing the hand from the impression ingv a' polymerized vinyl-resin dispersed'in a plas-- ticizer therefor, and which gels at a temperature below the liquefying temperature of the alginate to form a flexible, elastic gel, congealing the resin on the surfaces of the impression, removing residual ungelled resin from the impression while leaving the resulting flexible positive in the said impression, filling the resulting open, seamless, flexible positive with a molten wax composition having a low melting point, hardening the wax composition in the positive to rigidify the positive, removing the resulting rigidified positive from the said impression, rendering the rigid positive electrically conductive, suspending the rigid positive as cathode in an electroforming bath, electrodepositing metal from the bath onto the positive except on the exposed portion of the core until the positive is coated uniformly with the metal, thereby producing an open coating of metal on the positive, removing the coated positive from the bath, melting and draining the wax rigidifying composition from the coated positive through the opening in the coating, collapsing the flexible positive away from the coating metal, and withdrawing the collapsed positive through" the said opening thereby leaving a hollow metal mold replica of the positive adapted to receive a resinous glove composition for molding therein cosmetic gloves to cover prosthetic hands.

' 3. The process of producing hollow, seamless molds for reproducing objects of intricate shapes, which comprises immersing the initial object to be introduced into a liquid alginate bath composition which forms a stiff elastic gel when cong'ealed, effecting gelation of the composition about the object, removing the object from the gelled alginate bath, thereby leaving an initial impression of the object in the gelled alginate bath, introducing into the impression a fluid gelable resinous composition comprising essentially a, polymerized vinyl resin dispersed in a plasticizer therefor and having a gelation temperature below the melting point of the gelled bath, effecting gelation of the resin over the peripheries of the impression, withdrawing ungelled residual resin from the said impression, thereby producing a flexible open positive of the impression, filling the positive with a rigidifying core including a low melting point wax, removing the rigidified positive from the alginate impression, coating the positive exteriorly with an electrically conductive material while the core is still in the positive, suspending the resulting coated and rigid positive as a cathode in an electroforming bath, depositing metal on the positive until the positive is coated with the electrodeposited metal while controlling deposition of the metal to produce a uniformly thick coating of metal on the positive over all coated surfaces thereof, removing the electrodeposited form from the electroforming bath, melting out the rigidifying core through an opening in the coating corresponding to an uncoated portion of the positive, collapsing the flexible positive away from the deposited metal, and removing the resulting collapsed positive through the said opening, thereby leaving the deposited metal as a rigid, hollow metal mold interiorly duplicating all details of the initial impression.

4. The process of making hollow, seamless, metal molds for duplicating objects of intricate shape, which comprises immersing an object to be duplicated in a gelable but fluid bath of an alginate composition, effecting gelation of the bath around and on the object to be duplicated, removing the object from the resulting gelled l2 bath thereby leaving an open, gelled initial im= pression of the object, introducing into the impression a gelable resinous composition comprisinga fiowable mixture of polymerized vinyl resin and a plasticizer therefor and having a gelation temperature below the melting point of the gelled alginate bath, to yield upon gelation a flexible elastic resin gel, heating the resinous composition in the impression until peripheral gelation of the resinous composition is efiected on the surfaces of the impression, rem oving ungelled resinous composition from the impression, thereby leaving an open resinous positive of the object of the impression, rendering the resulting flexible positive rigid by introducing therein a liquid low melting point core material and solidifying the core material in the positive, removing the positive from the impression, applying a coating of electrically conducting material to the exterior surface of the positive, introducing the rigidified positive as a cathode in an electroforming bath, electrodepositing metal on the coated surfaces of the positive, thereby producing a seamless, open electrcdeposit on the positive, removing the resulting electrolytically coated positive from the electroforming bath, melting the core, draining the resulting molten core material from the electroformed metallic coating, collapsing the flexible resinous positive from the said metallic coating, and removing the collapsed resinous positive from the interior of the said coating through the opening therein, ther by leaving the coating as a rigid, hollow, seamless, metal mold interiorly duplicating all surface details of the initial impression of the object being reproduced.

CLARE L. MILTON, JR.

CARL A. NIELSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,296,498 Fodor Mar. 4, 1919 2,124,871 Beal July 26, 1938 2,275,582 Bull Mar. 10, 1942 OTHER REFERENCES Molding and Casting, by Carl Dome Clarke, 2nd ed., 1946, pp. -138, 291-294.

Acrylics, by S. D. Tylman and F. A. Peyton, 1946, pp. 141-144. 

1. IN THE PRODUCTION OF SEAMLESS COSMETIC GLOVES FOR COVERING PROSTHETIC HANDS, THE STEPS WHICH COMPRISE IMMERSING A MODEL NATURAL HAND IN A CONGEABLE LIQUID ALGINATE COMPOSITION WHICH FORMS A STIFF, ELASTIC GEL WHEN CONGEALED, CONGEALING THE COMPOSITON AROUND THE HAND AND ADJACENT ARM PORTIONS, THEREBY PRODUCING AN IMPRESSION IN THE CONGEALED ALGINATE GEL WHICH DUPLICATES ALL SURFACE CHARACTERISTICS OF THE MODEL HAND, REMOVING THE HAND FROM THE IMPRESSION WITHOUT PERMANENTLY DISTORTING THE IMPRESSION AND LINE THEREIN DUPLICATING THE SURFACE CHARACTERISTICS OF THE MODEL HAND, PRODUCING AN OPEN, FLEXIBLE POSITIVE OF THE MODEL HAND FROM THE SAID IMPRESSION BY FILLING THE IMPRESSION WITH A CONGEALABLE LIQUID RESINOUS COMPOSITION INCLUDING A POLYMERIZED VINYL RESIN DISPERSED IN A PLASTICIZER THEREFOR, AND WHICH GELS AT A TEMPERATURE BELOW THE LIQUEFYING TEMPERATURE OF THE ALIGNATE TO FORM FLEXIBLE, ELASTIC GEL, CONGEALING THE RESIN ON THE PERIPHERY OF THE IMPRESSION, REMOVING RESIDUAL UNGELLED RESIN FROM THE IMPRESSION WHILE LEAVING THE RESULTING FLEXIBLE POSITIVE IN THE SAID IMPRESSION, FILLING THE RESULTING OPEN, SEAMLESS, FLEXIBLE POSITIVE WITH A READILY REMOVABLE RIGIDIFYING CORE, REMOVING THE RESULTING RIGIDIFIED POSITIVE FROM THE SAID IMPRESSION, RENDERING THE POSITIVE ELECTRICALLY CONDUCTIVE, ELECTRODEPOSITING A MOLD METAL ON THE RIGID POSITIVE EXCEPT OVER PORTIONS OF THE CORE EXPOSED BY THE OPENING IN THE POSITIVE, THEREBY PRODUCING AN OPEN, ELECTRODEPOSITED MOLD FORM THROUGH THE OPENING IN WHICH THE CORE AND FLEXIBLE POSITIVE CAN BE REMOVED, AND REMOVING THE CORE AND FLEXIBLE POSITIVE FROM THE ELECTRODEPOSITED METAL THROUGH THE SAID OPENING, THEREBY LEAVING A HOLLOW SEAMLESS, OPEN METALLIC MOLD INTERIORLY DUPLICATING THE SURFACE CHARACTERISTICS OF THE ORIGINAL MODEL HAND. 